ARCHIVED REPORTS_XR0012175 - Laserfiche WebLink

Home Browse Search

f The following were the findings from the soil and groundwater investigation Groundwater was first encountered at a depth of about 45 feet in the test borings • The groundwater flow is generally in an easterly direction of flow across the site at a moderately flat gradient varying from 0 002 to 0 005. • Groundwater samples from MW2 during 1989 and 1990 showed benzene concentrations ranging from 5.0 to 8 2 mg/1 benzene, 1.1 to 4.0 mg/1 of toluene, 1.1 -'' to 2 2 mg/l of ethylbenzene, and 4 6 to 8.5 mg/1 of xylene • Groundwater samples from MW 1, MW3, and MW4 showed detectable levels of TPH and BTEX • Groundwater samples collected in 1989 from MW5 showed low TPH levels, but indicated the highest level of benzene at 15 mg/l, toluene of 4 5 mg/1, ethylbenzene of 2 1 mg/l, and xylene of 4 8 mg/l • Also, low levels of 1,2-dichloroethane (DCA) showed up in MW4 and MW6 and 1,2-dichloropropane showed up in groundwater samples from MW6 These compounds were never tested before from any of the monitoring wells or in the soil borings m Soil boring TB5 located in the northwest corner of the property, indicated significant concentrations of benzene, toluene, xylene, and ethylbenzene (BTEX) and TPH as gasoline. Soils to a depth of 15 feet indicated no concentrations of BTEX and TPH as gasoline But soils encountered at depths of 15 to 25 feet showed TPH at 12000 mg/kg, and maximums of benzene at 0 008 mg/kg, toluene at 1.7 mg/kg, xylene at 50 mg/kg,and ethylbenzene at 16 mg/kg All other soil bonngs,TB6, TB7,TB8,TB9, MW4 and MW5 showed non detect concentrations of TPH and BTEX • Soil samples collected from SB21 and SB23 showed non-detectable levels of hydrocarbons Samples from SB22 from 15 to 45 feet showed detectable levels of hydrocarbons. SB21 was later converted to a monitoring well, MW6. Groundwater from MW6 showed low levels of hydrocarbons Conclusions drawn from this investigation was that monitoring wells along the eastern edge of the property(downgradient direction) show a significant increase in dissolved petroleum hydrocarbons across the site Downgradient monitoring wells MW2 and MW5 contain high levels of hydrocarbons This suggests that contaminated groundwater may be moving offsite. The fact that MW 1, MW3, and MW4 also show detectable levels of BTEX, showing evidence of an offsite source of contamination 5